The pavement begins to warm under the summer Colorado sun as Michael Sandler jogs up Flagstaff Road near Boulder. Normally, this shouldn’t concern a runner. Sandler, however, is jogging barefoot.

“When you are barefoot, you are forced to run the way ancient man ran, which is a soft dance,” Sandler said. “Even my upper body got stronger.”

He claims he can run farther and with less chance of injury now that he has left his running shoes in the closet. He’s far from the only runner who believes so. The number of barefoot runners appears to be a growing niche among the running community. Those who run barefoot maintain it helps them keep a stride that delivers less shock to the foot, helping prevent injuries.

But experts caution that only a small percentage of runners can successfully train sans shoes.

“Your muscles, tendons and bones are balanced if your shoe is properly fit and your foot is properly supported,” said Eugene Rosenthal, a local podiatrist, who said he would never recommend running barefoot.

The concept of running without shoes can be hard to wrap your mind around, mainly because so few people in this country have ever tried it.

“I would say 98 percent of the U.S. do not grow up barefoot, walking barefoot, going to school barefoot,” said Mark Plaatjes, a physical therapist and owner of Boulder Running Company. “If you do not grow up barefoot, it is a really difficult thing to do.”

But Ethiopian Abebe Bikila did grow up running barefoot, and he won the 1960 Olympic marathon in Rome unshod.

The beauty of running barefoot, say its true believers, is that your feet will adapt naturally to almost any surface.

“You have to start very slow, like a baby that is starting to walk,” Sandler said. “When you start slow, you will find a natural stride that is the softest, most efficient way to move, because you are feeling the ground.”

Mr. Natural goes barefoot

Most runners who come into Plaatjes’ store have one thing in common. Their feet are giving them problems. And barefoot running will do nothing to solve that, he said.

“They come here for us to fix the problems,” said Plaatjes, who won the marathon at the 1993 world championships. “If we let them run barefoot, it’s not going to work. It’s not going to be pretty.”

They want help dealing with issues regarding their feet, or suggestions on their running stride, and they come to Plaatjes for guidance. Most require the aid of either specialty shoes to train in or orthotics, which are custom-made inserts that go in a shoe and support the foot.

“They say if you wear an orthotic it’s like wearing a cast, you don’t allow the foot to move,” Plaatjes said. “Not true, not true at all. We are trying to limit excessive motion.”

But Ivo Waerlop, a Summit County chiropractor, begs to differ.

“The major problem with footwear is there is little activation of intrinsic muscles of feet,” said Waerlop, who does some form of barefoot training with many of his clients.

Barefoot running allows muscles to strengthen and work in different ways than they are familiar with while in shoes, Waerlop said. Runners experience a more natural stride when they are barefoot, he said. When in training shoes, runners are more likely to land on their heel before rocking through to the toes, he believes. Without shoes, the forefront of the foot takes the brunt of the force, but then the calf muscle gently lowers the heel, creating a softer stride.

“When you take away the feeling of the impact of your feet hitting the ground, you end up putting much more impact into your body than if you felt it and adjusted your stride,” said Barefoot Ted, perhaps the most well-known barefoot running enthusiast. He lives in Washington and has spread the gospel of barefoot running for five years.

“The more padded the shoe has become, the more impact people are putting into their body,” Barefoot Ted said.

Sandler, who lives in Boulder, agrees. “I hit on the balls of my feet,” he said. “It gives me the ability to roll my foot and make constant adjustments for a good stride.”

Sandler runs an average of 80 miles a week and does approximately 70 percent of his distance barefoot. Like most dedicated barefoot runners, he’s developed thick calluses on his feet.

No shoes = bigger smiles

But Barefoot Ted and Sandler are on the extreme side of the barefoot spectrum. Most runners who do barefoot training log a few miles a week but do most of their training with shoes.

“I can definitely feel, even when I’m in my shoes, I’m more aware of my foot strikes,” said Jeremy Grev, who is training for the 5430 Long Course Triathlon in Boulder. “I feel better and more efficient on my runs.”

Grev is a local trainer and isn’t the only one who wants to help people learn the barefoot method. Sixteen runners came together at Martin Park in Boulder last Saturday for the first meet-up of the Barefoot Running Club, hosted by Sandler.

“It was like watching kids at the park,” he said. “Everyone had a beaming, ear-to-ear smile on their face.”

The group went through a variety of foot-strengthening exercises, including scrunching their toes and walking on coarse sand in a nearby playground. After the runners had dispersed, the message board on the meet-up site was hot with comments.

“A fantastic and just downright fun experience,” wrote Scott.

According to Sandler, participants were already trying to set up weekly runs outside of the Saturday meet-up.

“We are on some sort of a beginning of a wave. It seems like it’s going to really take off.”

The trendsetters

Ethiopian Abebe Bikila won the 1960 Olympic marathon running barefoot through the cobblestone streets of Rome.

South African Zola Budd is best known for her controversial 3,000-meter race at the 1984 Olympics in Los Angeles, where some say she bumped American runner Mary Decker, causing Decker to fall.

Charlie “Doc” Robbins won two USA National Marathon Championships in the late 1940s.

No bare tootsies in high school

Rules concerning barefoot running:

CHSAA: Colorado high school runners must race in shoes.

NCAA: College and university runners may compete in bare feet.

USA Track and Field: A competitor may compete in bare feet or with footwear on one or both feet.

Barely there

A look at state-of-the-art shoes that might make it feel like you’re running barefoot.

Nike Free 5.0

You can practically fold the Nike Free in half it’s so flexible. The shoe, which weighs 8.5 ounces, tries to imitate running barefoot while providing protection from the elements and some cushioning.

Vibram FiveFingers

The FiveFingers might look weird on your feet, but barefoot runners who don’t want to bare it all swear by this quasi-shoe, which weighs five ounces. It has individual toe compartments and a thin sole. There is no cushioning, so you will maintain the same stride as you would if you were sans shoes.

The barefoot spectrum

Types of barefoot runners

1. The “I’m never wearing shoes again” type

These are the people who run most of their miles without shoes and enjoy being barefoot during the day when they aren’t hitting the pavement or the trail. A tiny fraction of runners.

2. The “This feels good” type

This group of runners will train several days a week barefoot, but still do some runs with shoes.

3. The “I enjoy a run on the golf course now and then” type

These people understand the benefits of strengthening their muscles by taking a cruise around a golf course or football field unshod, but do the majority of their running with shoes.

4. The “You’ll never get me to go barefoot” type

These are people who do not have the foot structure to run barefoot without getting injured.

This article has been corrected in this online archive. Originally, due to a reporting error, it said Jeremy Grev was working with a trainer. Grev is a local trainer who is teaching the barefoot method.